Small tractors, usually of the lawn and garden variety, have become quite sophisticated. Hydraulic systems, electrical systems and transmissions, even of the four wheel drive variety, are now provided on these tractors. A problem associated with providing these features is that there are space limitations on the tractors which make it very difficult to find protective areas for them. Therefore, it is often necessary to use one structure to serve two functions whereas in larger tractors there would be two structures to serve each of the individual functions. An example of this is on a small tractor mounted mower in which the tractor seat may be raised to a position to permit other operating parts of the tractor to be exposed for maintainance and inspection. For example, there may be a transmission or several drive shafts, hydraulic systems and batteries underneath the location of the seat. The seat frame, when raised, provides the only opening through which these parts under the seat can be serviced. The structure for locking the seat in its up position must be very simple and must not create a situation where that structure interferes with other parts of the tractor, particularly when the seat is in its down position.
In a previous U.S. Pat. No. 4,565,407 which issued to the present inventor on Jan. 21, 1986, there is provided a seat holdup mechanism that is mounted on a small tractor. The holdup mechanism consists of a seat frame in the form of a plate that may be moved vertically to open up the area under the seat. Mounted on the underside of the seat frame is a series of teeth that receives the upper end of a latch rod. The lower end of the latch rod is pivotally mounted on the vehicle beneath the seat location. A spring extends between the seat and the rod and tends to hold the upper end of the latch rod into engagement with the teeth. The teeth are formed in a pair of vertical plates spaced apart on the underside of the frame. A rod releasing device extends from these plates outwardly and through the seat frame so that a person may release the rod from the teeth to permit the seat to be lowered.
One of the problems with the seat shown in U.S. Pat. No. 4,565,407 is that the vertical plates that have the teeth cut therein extend downwardly, and when the seat is positioned in its down position, the plates extend into the area of the tractor where other parts of the tractor, such as those mentioned above, may be positioned. Since there is a very limited area on the tractor, these plates take up room which could otherwise be used. Also, the rod that latches the seat in its upper position must also swing in a vertical plane requiring additional clearance. Further, the idea of having teeth exposed with a portion of the rod that may ratchet against those teeth creates somewhat of a hazardous condition and it would be preferable that such teeth not be in the location where a person could place his hands or get clothing caught.